usb: phy: handle phy related regulators properly

Currently driver is enabling all the regulators in probe
even if usb cable is not connected which has power impact.
Hence enable regulators before the phy initialization sequence
and move regulator_set_voltage & enable/disable API for vdd supply
in msm_ssusb_qmp_ldo_enable() to handle all the regulators from one
place.

Change-Id: Ibc4cf8328c209dbf968b7d6c498e1462397be351
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>